玖、發明說明: 【發明所屬之技術領域】 本發明係關於一種半導體發光元件及其製程,並 且特別地,該半導體發光元件包含一強健的歐姆層形 成於一最頂層半導體材料層與一透明導電氧化物材料 層之間,藉此使得該半導體發光元件具有較低並且穩 定的正向電壓。 【先前技術】 透明導電氧化物材料(Transparent conductive oxide),例如,ITO、ZnO、InO或ZrO 等…材料,已被用來披覆在半導體發光元件的表面。 披夜在半導體發光元件之表面上的透明導電氧化物材 料層(Transparent conductive oxide layer, TCOL),其主要功用係做為導電視窗層,以利電流散 佈,並且讓光線穿透,來提昇半導體發光元件的外部 量子效率(External quantum efficiency)。 然而,由於透明導電氧化物材料層與最頂層半導 體材料層(例如,P型態GaN層)之間的歐姆接觸並非是 件容易的工作,此類披覆透明導電氧化物材料層之技 1229952 術的主要關注點即在於如何達到低並且穩定的正向電 壓(Vf)。以下將詳述數個先前技術,並且說明此類技 術的困難性。说明 Description of the invention: [Technical field to which the invention belongs] The present invention relates to a semiconductor light emitting element and a process for the same. In particular, the semiconductor light emitting element includes a strong ohmic layer formed on a topmost semiconductor material layer and a transparent conductive layer. Between the oxide material layers, the semiconductor light-emitting element has a low and stable forward voltage. [Previous Technology] Transparent conductive oxide materials, such as ITO, ZnO, InO, ZrO, etc., have been used to cover the surface of semiconductor light emitting elements. The transparent conductive oxide layer (TCOL) layer on the surface of the semiconductor light-emitting element is mainly used as a conductive window layer to facilitate the spread of current and allow light to penetrate to enhance semiconductor light emission. External quantum efficiency of the device. However, since the ohmic contact between the transparent conductive oxide material layer and the topmost semiconductor material layer (for example, a P-type GaN layer) is not an easy task, such a technique for coating the transparent conductive oxide material layer is 12299952. The main concern is how to achieve a low and stable forward voltage (Vf). Several previous technologies are detailed below and the difficulties of such technologies are explained.
Okazaki等人於美國專利第5, 977, 566號專利中 提出於一 I TO層與一 P型態GaN接觸層之間施加一金屬 中介層(Agent layer),進而減少導電帶的偏移。形 成上述中介層的材料包含Mg、冲i、Au、Zu以及Ti。 藉此,半導體發光元件的正向電壓(Vf)係被降低❶此 外’*^叫-:^111111等人於美國專利第6,078,064號專 利中提出高摻雜濃度(高於5x1018)的P型態接觸層 (例如’ InGaN、GaAs、AiGaAs或GaP)做為中介層。 Suzuki等人於美國專利第6, 479, 836號專利中提出選 擇性地摻雜高濃度p型態載子,以形成超晶格(Super_ lattice),例如,lnGaN/GaN、AlGaN/GaN 或是其 他組合,進而得到較低的正向電壓(Vf)。此外,亦有 人提出以Ni做為中介層,並且藉由IT〇層中被擴散的 氧’進而轉換為NiO層,藉以降低半導體發光元件的 正向電壓(Vf)。 然而’於上述利用中介層的技術中,若不是中介 層本身會吸收半導體發光元件的輸出光強度。再不然 就是於操作期間,因為中介層的高摻雜濃度造成造成 載子於中介層與接觸層之間擴散,導致半導體發光元 件的正向電壓(Vf)極可能不穩定。 7 I TO層做為電流散佈層以提昇半導體發光元件所輸 出的光強度,並且覆蓋於一般的Ni/Au透明導電層 (Transparent conductive layers, TCLs)之 上,已為習知的製程。例如,Oberman等人於美國專 利第5, 925897號專利中提出於I TO層與P型態InGaN接 觸層之間形成一極薄的Au/Ni複合層。此外,Lin等人 於美國專利第6, 465, 808號專利中提出點狀的透明導 電層。因為點狀的透明導電層真有較少的吸收區域, 進而讓更多由半導體發光元件所發射的光輸出。 1^11(1〇^56於美國專利第6,287,947號專利中提出於 I TO層與P型態GaN接觸層之間形成多層的透明導電 層。然而,上述技術之問題在於因為磊晶晶圓之表面 粗綠度的差異或是氫氣鈍化效應(Hydrogen passivation effect),使得半導體發光元件之正 向電壓(Vf)以及照度(Iv)的再現性相當差。 雖然,有許多不同型態的歐姆接觸層,可以執行 與IT0層或是透明導電氧化物層接觸之功用。然而, 上述的歐姆接觸層皆為高濃度的N型態摻雜或是P型態 摻雜。在半導體發光元件的製造過程中,製程的環 境,像是殘留的氧氣或是氫元素,極容易影響到歐姆 接觸層的效能。半導體發光元件的正向電壓(Vf)也會 因為歐姆接觸層品質的不穩定而造成偏移。 因此,本發明之一目的在於針對一半導體發光元 1229952 、 件提供一強健的歐姆層,藉此使該半導體發光元件具 有較低並且穩定的正向電壓。 【發明内容】 根據本發明之一較佳具體實施例之半導體發光元 件,包含一半導體基材、一形成於該半導體基材上之 多層結構、一覆蓋該多層結'構之無摻雜膜以及一覆蓋 該無摻雜膜之透明導電氧化物材料層。該多層結構包 含一發光區。該無摻雜膜係由一 InxGayAlzN材料形 成,其中x+y + z=l,並且OSx,y,zSl。該半導體發 光元件之一正向電壓係低於或等於3. 7伏特。 根據本發明之一較佳具體實施例製造一半導體發 光元件的方法,首先,一多層結構係形成於一半導體 基材上。該多層結構包含一發光區。該多層結構提供 一最頂層半導艎材料層。接著,一無摻雜膜係形成並 且覆蓋該最頂層半導體材料層。該無摻雜膜16係由一 InxGayAl2N材料並且藉由一磊晶製程所形成,其中 x + y + z = l,並且0 S X,y,z S 1。最後,一透明導電氧 化物材料層係形成並且覆蓋該無摻雜膜,以完成該半 導體發光元件。 關於本發明之優點與精神可以藉由以下的發明詳 述及所附圖式得到進一步的瞭解。 9 1229952 【實施方式】 根據本發明之一較佳具體實施例之半導體發光元 件ίο係揭示於圖一中,圖一係以截面視圖描述該半導 體發光元件10之結構。 如圖一所示,該半導體發光元件10包含一半導體 基材12、一形成於該半導體基材12上之多層結構 (Multi-layer structure)14、一覆蓋該多層結構 14之無摻雜膜(Undoped film)16以及一透明導電氧 化物材料層18。 特別地,該多層結構包含一發光區(Light emitting region),例如,一 PN 接合(PN-junction)、 一雙異質接合(Double hetero-junction),或是一多重量子井(Multiple quantum we 11 ) «> 特別地,該無摻雜膜16係由一 InxGayAlzN材料形 成,其中x + y + z = l,並且〇gx,y,zSl。於一具體實 施例中’該無摻雜膜1 6係以藉由一磊晶製程所形成, 並且該無推雜16膜之一厚度係小於或等於2〇埃。 如圖一所示,該多層結構14包含一最頂層半導體 材料層142 ’該最頂層半導體材料層142係與該無摻雜 膜16接觸。於一具體實施例中,該最頂層半導體材料 10 層 142係選自 GaN、AlGaN、InGaN,或是 InGaAIN 以 及相類似材料中之一材料所形成。然而,用以形成該 最頂層半導體材料層142的材料必須可以匹配該多層 結構14。 於一具體實施例中,該透明導電氧化物材料層18 係由選自ITO、ZnO、InO以及ZrO以及相類似材料中 之一材料所形成。 、 製造圖一中所繪示之半導體發光元件10之方法係 揭不於圖《一 A至圖^一 C’同樣地,該等圖式係以截面視 圖描述製造過程中的中間產物以及最終的產物。 首先,如囷二A所示,由多層依序形成的磊晶層所 組成的多層結構14形成於該半導體基材12上。特別 地,該多層結構14包含一發光區,例如,一PN接合、 一雙異質接合,或是一多重量子井。 同樣示於圖二A,該多層結構14提供該最頂層半導 體材料層142。 接著,如圖二B所示,該無摻雜膜16係形成並且覆 蓋該最頂層半導體材料層142。特別地,該無摻雜膜 16係由一 inxGayAlzN材料並且藉由一磊晶製程所形 成,其中x+y + z = l,並且。於磊晶成長 •1229952 過程中,該無摻雜膜16的厚度係控制在小於或等於20 埃。 最後,如圖二C所示,該透明導電氧化物材料層18 係形成並且覆蓋該無摻雜膜16,以完成該半導鱧發光 元件10。 於本發明中,該、無摻雜InxGayAl2N材料膜16係做 為一接觸層,若形成該最頂層半導體材料層142為氮 化物半導辞材料,該無摻雜層16進而形成氮化物半導 體材料142與透明導電材料層18之間的良好歐姆連 接。於此例中,形成該透明導電氧化物層之材料可以 是ITO、ZnO、InO、ZrO,或是其他功函數高過3. 6eV 或電子親和力能階高過IruGayAlzN材料膜之電子親和 力能階的透明導電氧化物材料。 於本發明中,該無摻雜InxGayAlzN材料膜亦係做 為穿遂層(Tunneling layer)。圖三所示,因為,做 為穿隧膜之無摻雜膜16相當薄320埃),致使橫跨該 穿隧膜16之電場於順向偏壓的情況下,將讓電子從價 電子帶162穿隧到導電帶164,並且回到該透明導電氧 化物材料層18上。圖三中的標號匕為費米能量 (Fermi’ s energy)。此外,根據本發明之半導體發 光元件因為沒有如同前案隱含的額外能障以及逆向能 障,因此,根據本發明之半導體發光元件之正向電壓 12 1229952 會較低。該正向電壓係由下列公式決定:Okazaki et al., In U.S. Patent No. 5,977,566, propose to apply a metal interlayer (Agent layer) between an I TO layer and a P-type GaN contact layer to reduce the offset of the conductive tape. The material for forming the above interposer includes Mg, Ni, Au, Zu, and Ti. As a result, the forward voltage (Vf) of the semiconductor light-emitting element is reduced. In addition, '* ^ called-: ^ 111111 and others proposed a P-type with a high doping concentration (higher than 5x1018) in US Patent No. 6,078,064 A contact layer (such as' InGaN, GaAs, AiGaAs, or GaP) is used as an interposer. Suzuki et al. Proposed in US Patent No. 6,479,836 to selectively dopant p-type carriers at a high concentration to form a super lattice, such as lnGaN / GaN, AlGaN / GaN, or Other combinations, in turn, result in a lower forward voltage (Vf). In addition, it has also been proposed that Ni be used as an interposer, and the diffused oxygen 'in the IT0 layer is further converted into a NiO layer, thereby reducing the forward voltage (Vf) of the semiconductor light emitting element. However, in the above-mentioned technology using an interposer, if the interposer itself does not absorb the output light intensity of the semiconductor light emitting device. Otherwise, during operation, due to the high doping concentration of the interposer, carriers diffuse between the interposer and the contact layer, and the forward voltage (Vf) of the semiconductor light-emitting device is likely to be unstable. The 7 I TO layer is used as a current spreading layer to enhance the light intensity output by the semiconductor light emitting element, and it is covered on the general Ni / Au transparent conductive layers (TCLs), which is a conventional process. For example, Oberman et al., In U.S. Patent No. 5,925,897, propose to form an extremely thin Au / Ni composite layer between the I TO layer and the P-type InGaN contact layer. In addition, Lin et al., U.S. Patent No. 6,465,808, proposed a dot-shaped transparent conductive layer. Because the dot-shaped transparent conductive layer really has less absorption area, so that more light emitted by the semiconductor light emitting element is output. 1 ^ 11 (1〇 ^ 56 in US Patent No. 6,287,947 proposed to form a multilayer transparent conductive layer between an I TO layer and a P-type GaN contact layer. However, the problem with the above technology is that the epitaxial wafer The difference in rough greenness of the surface or the hydrogen passivation effect makes the reproducibility of the forward voltage (Vf) and illuminance (Iv) of the semiconductor light emitting device quite poor. Although there are many different types of ohmic contact layers It can perform the function of contacting the IT0 layer or the transparent conductive oxide layer. However, the above-mentioned ohmic contact layers are all N-type doped or P-type doped at a high concentration. In the manufacturing process of the semiconductor light emitting device The process environment, such as residual oxygen or hydrogen, can easily affect the performance of the ohmic contact layer. The forward voltage (Vf) of the semiconductor light-emitting element will also be shifted due to the unstable quality of the ohmic contact layer. Therefore, an object of the present invention is to provide a robust ohmic layer for a semiconductor light-emitting element 12299952, thereby enabling the semiconductor light-emitting element to have a low and stable positive [Summary of the Invention] A semiconductor light emitting device according to a preferred embodiment of the present invention includes a semiconductor substrate, a multilayer structure formed on the semiconductor substrate, and a non-doped layer covering the multilayer structure. A doped film and a transparent conductive oxide material layer covering the undoped film. The multilayer structure includes a light emitting region. The undoped film is formed of an InxGayAlzN material, where x + y + z = 1, and OSx, y, zSl. A forward voltage of one of the semiconductor light-emitting elements is lower than or equal to 3.7 volts. According to a preferred embodiment of the present invention, a method for manufacturing a semiconductor light-emitting element, first, a multilayer structure is formed on On a semiconductor substrate. The multilayer structure includes a light emitting region. The multilayer structure provides a topmost semiconductor material layer. Next, an undoped film system is formed and covers the topmost semiconductor material layer. The undoped film The 16 series is formed by an InxGayAl2N material and an epitaxial process, where x + y + z = l, and 0 SX, y, z S 1. Finally, a transparent conductive oxide material layer system is formed and covered The non-doped film is used to complete the semiconductor light emitting device. The advantages and spirit of the present invention can be further understood by the following detailed description of the invention and the attached drawings. 9 1229952 The semiconductor light emitting element of the preferred embodiment is disclosed in FIG. 1. FIG. 1 is a cross-sectional view describing the structure of the semiconductor light emitting element 10. As shown in FIG. 1, the semiconductor light emitting element 10 includes a semiconductor substrate 12, a A multi-layer structure 14 formed on the semiconductor substrate 12, an undoped film 16 covering the multi-layer structure 14, and a transparent conductive oxide material layer 18. In particular, the multilayer structure includes a light emitting region, for example, a PN junction, a double hetero-junction, or a multiple quantum well (Multi quantum we 11). ) «≫ In particular, the undoped film 16 is formed of an InxGayAlzN material, where x + y + z = 1 and 0 gx, y, zSl. In a specific embodiment, the undoped film 16 is formed by an epitaxial process, and a thickness of one of the undoped 16 films is less than or equal to 20 angstroms. As shown in FIG. 1, the multilayer structure 14 includes a topmost semiconductor material layer 142 ′. The topmost semiconductor material layer 142 is in contact with the undoped film 16. In a specific embodiment, the topmost semiconductor material 10 layer 142 is formed from a material selected from GaN, AlGaN, InGaN, or InGaAIN and similar materials. However, the material used to form the topmost semiconductor material layer 142 must match the multilayer structure 14. In a specific embodiment, the transparent conductive oxide material layer 18 is formed of a material selected from the group consisting of ITO, ZnO, InO, ZrO, and the like. 2. The method of manufacturing the semiconductor light emitting element 10 shown in Figure 1 is not shown in the drawings "A to Figure ^ C '. Similarly, these drawings are cross-sectional views describing the intermediate products in the manufacturing process and the final product. First, as shown in FIG. 2A, a multilayer structure 14 composed of a plurality of sequentially formed epitaxial layers is formed on the semiconductor substrate 12. Specifically, the multilayer structure 14 includes a light emitting region, such as a PN junction, a double hetero junction, or a multiple quantum well. Also shown in FIG. 2A, the multilayer structure 14 provides the topmost semiconductor material layer 142. Next, as shown in FIG. 2B, the undoped film 16 is formed and covers the topmost semiconductor material layer 142. Specifically, the undoped film 16 is formed of an inxGayAlzN material and an epitaxial process, where x + y + z = l, and. During epitaxial growth • 1229952, the thickness of the undoped film 16 is controlled to be less than or equal to 20 angstroms. Finally, as shown in FIG. 2C, the transparent conductive oxide material layer 18 is formed and covers the undoped film 16 to complete the semi-conducting erbium light-emitting element 10. In the present invention, the undoped InxGayAl2N material film 16 is used as a contact layer. If the topmost semiconductor material layer 142 is a nitride semiconductor material, the undoped layer 16 further forms a nitride semiconductor material. Good ohmic connection between 142 and transparent conductive material layer 18. In this example, the material forming the transparent conductive oxide layer may be ITO, ZnO, InO, ZrO, or other work functions having a higher work function than 3.6 eV or an electron affinity level higher than the electron affinity level of the IruGayAlzN material film. Transparent conductive oxide material. In the present invention, the undoped InxGayAlzN material film is also used as a tunneling layer. As shown in FIG. 3, because the undoped film 16 as the tunneling film is quite thin (320 angstroms), so that the forward electric field across the tunneling film 16 will cause electrons to pass through the electron band. 162 tunnels to the conductive strip 164 and returns to the transparent conductive oxide material layer 18. The numbered dagger in Figure 3 is Fermi ’s energy. In addition, since the semiconductor light emitting element according to the present invention does not have additional energy barriers and reverse energy barriers as implied in the previous case, the forward voltage 12 1229952 of the semiconductor light emitting element according to the present invention will be low. The forward voltage is determined by the following formula:
Vf = EXP( -4(2m*^Eg3)3/2Vf = EXP (-4 (2m * ^ Eg3) 3/2
HE 其中,m*係等效電子或電洞質量,厶係該無摻雜膜之 等效能帶隙,e係電子電荷,G係布朗克常數,並且万 係跨越該無摻雜膜之電場。 表一中係列舉數個實際案例以及其正向電壓與照 度。明顯地,表一中列舉的案例其正向電壓係為命理 的低電壓(3.3V〜3.7V),並且就照度而言,皆為高亮 度的半導體發光元件。另外,就技術觀點而言,誠信 本發明所提供最為歐姆層的無摻雜膜可適用於其他未 在本專利說明書中所提及表面彼覆TCOL的半導體發光 元件。 13 1229952 表一 TCOL 之 材料 歐姆層之材料 (皆為無摻雜) 最頂層之半導 體材料 作用層(亦即發 光區)之材料 正向電壓 (V) 照度 (mcd.) IT0 I IlxG3yA 1 zN P型態GaN InGaN 3. 3 800 ZnO InxGayAlzN 型態GaN InGaN 3. 7 650、 InO I rixGByA 1 zN P型態GaN InGaN 3. 5 710 ZrO I IlxGByA 1 zN P型態GaN InGaN 3. 6 690 明顯地,該無摻雜膜沒有摻雜P型態、N型態或共 同摻雜型態之載子。因此,於根據本發明之半導體發 光元件操作期間,載子擴散的情形不會發生。藉此, 根據本發明之半導體發光元件之正向電壓於操作期間 係保持穩定。 總結本發明的特徵以及優點茲列舉如下: (a) 於最頂層半導體材料層與TCOL之間,介入甚薄 的無摻雜InxGayAlzN膜,進而形成最頂層半導體 材料層與TCOL之間的良好歐姆連接; 14 1229952 (b) 無摻雜InxGayAlzN膜做為穿遂層,其厚度被控 制致使半導體發光元件之正向電壓達到合理的低 電壓;以及 (c) 由於無摻雜膜,於根據本發明之半導體發光元 件操作期間,載子擴散的情形不會發生,藉此, 根據本發明之半導體發光元件之正向電壓於操作 期間係保持穩定。 藉由以上較佳具體實施例之詳述,係希望能更加 清楚描述本發明之特徵與精神,而並非以上述所揭露 的較佳具體實施例來對本發明之範疇加以限制。相反 地,其目的是希望能涵蓋各種改變及具相等性的安排 於本發明所欲申請之專利範圍的範疇内。因此,本發 明所申請之專利範圍的範疇應該根據上述的說明作最 寬廣的解釋,以致使其涵蓋所有可能的改變以及具相 等性的安排。 【圖式簡單說明】 圖一係截面視圖,用以描述根據本發明之一半導 體發光元件的結構。 圖二A至圖二C係截面視圖,用以描述根據本發明 之一製造半導體發光元件的方法。 15 1229952 圖三係繪示於做為穿遂層的無摻雜InxGayAlzN# 料膜内,電子從價電子帶162穿隧到導電帶的情形。 【圖式標號說明】 10 :半導體發光元件12 :半導體基材 14 :多層結構 142 :最頂層半導體材料層 16 :無摻雜膜 162 :價電子帶 164 ··導電帶 18 :透明導電氧化物材料層 16HE where m * is the equivalent electron or hole mass, 厶 is the equivalent efficiency band gap of the undoped film, e is the electronic charge, G is the Bronck constant, and is the electric field across the undoped film. Table 1 lists several practical cases and their forward voltage and illuminance. Obviously, in the cases listed in Table 1, the forward voltage is a numerically low voltage (3.3V ~ 3.7V), and in terms of illuminance, they are all high-brightness semiconductor light-emitting elements. In addition, from the technical point of view, sincerity of the undoped film provided by the present invention as the most ohmic layer can be applied to other semiconductor light-emitting devices whose surfaces are not covered with TCOL in this patent specification. 13 1229952 Table 1 Materials of TCOL Materials of ohmic layer (all doped) Materials of topmost semiconductor material active layer (ie light emitting area) Forward voltage (V) Illuminance (mcd.) IT0 I IlxG3yA 1 zN P Type GaN InGaN 3. 3 800 ZnO InxGayAlzN Type GaN InGaN 3. 7 650, InO I rixGByA 1 zN P type GaN InGaN 3. 5 710 ZrO I IlxGByA 1 zN P type GaN InGaN 3. 6 690 Obviously, The undoped film is not doped with a carrier of a P-type, an N-type, or a co-doped type. Therefore, during the operation of the semiconductor light emitting element according to the present invention, the case of carrier diffusion does not occur. Thereby, the forward voltage of the semiconductor light emitting element according to the present invention remains stable during operation. The features and advantages of the present invention are summarized as follows: (a) A very thin undoped InxGayAlzN film is interposed between the topmost semiconductor material layer and the TCOL, thereby forming a good ohmic connection between the topmost semiconductor material layer and the TCOL. 14 1229952 (b) the undoped InxGayAlzN film is used as a tunneling layer whose thickness is controlled so that the forward voltage of the semiconductor light-emitting element reaches a reasonable low voltage; and (c) because of the undoped film, During the operation of the semiconductor light-emitting element, the situation of carrier diffusion does not occur, whereby the forward voltage of the semiconductor light-emitting element according to the present invention remains stable during the operation. With the above detailed description of the preferred embodiments, it is hoped that the features and spirit of the present invention may be described more clearly, rather than limiting the scope of the present invention with the preferred embodiments disclosed above. On the contrary, it is intended to cover various changes and equivalent arrangements within the scope of the patents to be applied for in the present invention. Therefore, the scope of the patent scope applied for by the present invention should be interpreted in the broadest sense according to the above description, so that it covers all possible changes and equivalent arrangements. [Brief description of the drawings] FIG. 1 is a cross-sectional view for describing a structure of a semiconductor light emitting element according to the present invention. FIGS. 2A to 2C are cross-sectional views for describing a method of manufacturing a semiconductor light emitting element according to one of the present invention. 15 1229952 The third series shows the electron tunneling from the valence electron band 162 to the conductive band in the undoped InxGayAlzN # material film as the tunneling layer. [Explanation of reference numerals] 10: semiconductor light emitting element 12: semiconductor substrate 14: multilayer structure 142: topmost semiconductor material layer 16: non-doped film 162: valence electron band 164 · conductive band 18: transparent conductive oxide material Layer 16